This study is examining the effects of family and ploidy on salinity tolerance of all-female populations of rainbow trout for net-pen aquaculture in Atlantic Canada. Triploidy renders fish sterile and therefore ensures that escaped fish cannot successfully breed in the wild, but triploids often have lower thermal tolerance than diploids. Conducted at the Huntsman Marine Science Centre (Saint Andrews, New Brunswick), this experiment used similarly sized sibling diploid and triploid females from the same eight families. After a two-month freshwater acclimation period at 13±1°C, fish were transitioned to seawater. Temperature was then gradually increased to 21°C at 1°C per day, decreased and maintained at 18°C for 10 days, and finally decreased at 1°C per day back to ambient temperature (7±1°C).
There was no effect of ploidy on plasma osmolality, but there was evidence of osmoregulatory difficulties (higher and more variable values) for both ploidies at 18°C in seawater (Figure 1). Additional data will be presented on plasma ion levels and interlamellar cell mass size (an indicator of osmorespiratory compromise) in these same fish. This study provides valuable insight into the physiological responses of sterile triploids to temperature and salinity challenges that can be encountered in aquaculture.